IRCT20150929024266N6 IRCT 2024-02-24 Tehran University of Medical Sciences Investigating the clinical response rate of patients with lower rectal cancer after combined treatment with intensity-modulated chemoradiotherapy and pre-surgical chemotherapy Evaluating the rate of complete clinical response following total neoadjuvant therapy by using chemoradiotherapy by Intensity modulated radiation therapy with simultaneous integrated boost (IMRT-SIB) in patients with lower rectal cancer; a Phase II randomized clinical trial 2024-01-06 anticipated 30 Complete https://irct.ir/trial/74567 interventional Randomization: N/A, Blinding: Not blinded, Placebo: Not used, Assignment: Single, Purpose: Treatment. 2 rectal cancer. The target population is people over 18 years of age with non-metastatic rectal cancer that are less than 5 cm from the anus and have good clinical conditions.Patients undergoing radiotherapy using 25-66/57 GTV, SIB and 25/45 CTV will receive five days a week (Saturday to Wednesday) and will be treated with chemotherapy regimen with Xeloda 825 2m/mg twice a day orally between The first to fourteenth days will be arranged. SIB-PTV will be gross tumor on MRI plus 1 cm of geometric margin. After radiotherapy, T3/4 or N+ patients undergo chemotherapy with one of XELOX or FOLFOX regimens. Examining the results of patients 12-16 weeks after the end of treatment will be done by MRI and colonoscopy.The MRI report must be reviewed by two people separately or reported by an experienced person. If there is a good response to the treatment and the tumor has decreased in size significantly, the chemotherapy is continued until 16 weeks are completed, and then a re-evaluation similar to the first evaluation is done. Patients with complete clinical response enter the Wait and W protocol if the patient agrees and other conditions are met (regular follow-up visits and surgeon's approval).Complete response means the absence of residual activity in MRI and the absence of tumor, ulcer or polyp in colonoscopy. If there is no suitable response, the patient will be referred for surgery and the rest of the chemotherapy will be done after the operation.. Undecided - It is not yet known if there will be a plan to make this available Justification or reason for indecision in sharing IPD is There is no further information